Figure 2: NAPQI and p-BQ are potent TRPA1 activators.

(a) Concentration-response relationship for [Ca²⁺]_i elevations produced by NAPQI in cells expressing mouse TRPA1 (left panel) and human TRPA1 (right panel). Data points are mean±s.e.m. of triplicate wells. (b) Pseudocoloured images illustrating [Ca²⁺]_i in DRG neurons before (background) and after challenges with NAPQI (500 nM) and 50 mM KCl. (c) Inward current activated by NAPQI (500 nM) in a mouse TRPA1–CHO cell (left panel) and the current–voltage relationship for TRPA1 stimulated by NAPQI (right panel). (d) Concentration-response curves for [Ca²⁺]_i responses produced by p-BQ in CHO cells expressing mouse TRPA1 (left panel) and human TRPA1 (right panel). Data points are mean±s.e.m. of triplicate wells. (e,f) Concentration-dependent amplitude and time course of currents elicited by p-BQ in mouse TRPA1-CHO cells (black trace 30 nM, blue 100 nM, red 300 nM and cyan 3 μM). Data in f are mean±s.e.m. of three to six experiments for each concentration. (g,h) Typical examples of [Ca²⁺]_i responses in DRG neurons cultured from Trpa1^+/+ (g) and Trpa1^−/− mice (h) produced by challenges with p-BQ (1 μM), allyl isothiocyanate (50 μM), capsaicin (1 μM) and K⁺ (50 mM). The scale bar represents 200 μm (b).